I have been thinking about Smith's claim in the opening arguments of the Wealth of Nations that the source of the Division of Labor is "the disposition to truck and barter." This has always puzzled me. He makes it clear that what he has in mind is disposition to truck and barter for its own sake. Why is such a disposition necessary in order for self-interested individuals to see the advantage of specialization and trade?
I have a suggested answer. In many potted histories of economic thought you may see a comparison of Smith and Ricardo on trade which says something like, " Smith focused on absolute advantage while Ricardo pointed to comparative advantage as the source of gains from trade." This seems to me to miss the point. What is distinctive about Smith on trade is that he makes the the differing advantages, absolute or comparative, that people have a consequence, instead of a cause, of specialization. By specializing we become differently skilled, though prior to specialization we are identical. This in turn reflects the fact that "the division of labor is limited by the extent of the market." A Portugal and England with identical resource endowments and identical increasing return technologies for producing wine and textiles can gain from specializing and trading. And it doesn't matter who makes the wine and who makes the textiles.
So here's my suggestion. If, prior to specialization, we are all pretty much alike, a disposition to truck and barter for its own sake, even where apparent gains from trade are negligible to non-existent, could get the specialization ball rolling.